I was reading a GTR-200 manual. The instructions for shield termination are specific; the pigtail must point toward the backshell where it exits the solder sleeve. Pointing away from the backshell and looping around to connect at the backshell bar is not allowed.

Dan - the answer is as Gil mentioned... Shorter ground wires mean shorter antennas to either pick up radiated emissions or to become a radiating element for emissions conducted from within the radio.

I've worked with some avionics equipment which had very specific shield termination requirements. The device would only meet EMI/RFI requirements when all the shield pigtails were fully contained within the all-metal backshell of the connector. What a bear those connectors were to work!

Dan - the answer is as Gil mentioned... Shorter ground wires mean shorter antennas to either pick up radiated emissions or to become a radiating element for emissions conducted from within the radio.

Well now, there's why I got curious. I understand we want to minimize the length of a conductor not covered by a shield. Here we're talking about shield braid and its pigtail to ground. In terms of radiating or receiving, you're saying the pigtail is somehow different from the entire shield braid, which is every bit as exposed?

Well now, there's why I got curious. I understand we want to minimize the length of a conductor not covered by a shield. Here we're talking about shield braid and its pigtail to ground. In terms of radiating or receiving, you're saying the pigtail is somehow different from the entire shield braid, which is every bit as exposed?

Yes.... they can become mini tuned antennae in short lengths. Keeping them really short limits the possible tuned frequencies.

This is one of Garmin's exhibition demonstrator panels. They remove a short length of the outer insulation, keeping the shield intact. Then they use a solder sleeve to attach their pigtail. All that happens about 4" away from the backshell. The shielding ends just before the cables enter the backshell. Now please don't ask me for a painless way of removing that outer insulation that neatly!

I took this photo in April 2017. If my memory serves me right (big "if" here), the panel they showed two years earlier had the wiring done the way they don't recommend now. I checked, but I didn't find any pictures.

Anyway, here is a link to one of their wiring videos showing how one can attach a pigtail to the shield. Pointing to the connector. Go figure ...

Funny because aircraft spruce, an authorized garmin dealer, does it the way Dan says garmin says is bad. Of course it behooves you to check and verify all connections as the 3 gtx345ís Iíve gotten from spruce with a harness all had miswired connections on an rs-232 port.

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